1. Field
This disclosure relates generally to trimming of semiconductor sensor devices, and more specifically, to a system, apparatus, and method for trimming two or more types of directionally-sensitive sensors in a package in parallel.
2. Related Art
The rapid growth in the use and availability of portable consumer electronic devices has brought about a corresponding growth in numbers and types of sensors associated with such devices. For example, many smart phone devices and tablet devices incorporate accelerometers, magnetometers, and gyroscopes to enable and enhance aspects of the user experience. In order to accommodate multiple types of sensors in a space conserving manner, sensor providers may include more than one type of sensor in a single semiconductor device package. Each type of sensor in a package must be calibrated, or trimmed, during the manufacturing process.
For multiple sensor packages, testing of each type of sensor is typically performed separately. For example, a package incorporating an accelerometer and a magnetometer can be tested and trimmed for response to gravity (for the accelerometer), and then tested and trimmed for response to a magnetic field (for the magnetometer). Such sequential testing can double the time necessary to test such packages. Current testing methods do not necessarily test and trim the multiple sensor package in an environment of use. For example, panels of un-singulated die can be accelerometer tested, but this does not provide the same package stress configuration as would be found during normal use (e.g., for singulated packages). This is an important issue because a typical accelerometer is a micro electromechanical systems package (MEMS), which has moving parts whose movement is sensitive to package stresses.
Another drawback of current testing methodology is that the sensor packages are oriented within the fields to which they respond (e.g., gravity) using complex gimbaled devices that can take significant time to position the device under test in a precise angle to the field of interest. Further, such complex devices can be both costly and resource intensive to maintain and support. In addition, the gimbal equipment used to orient the device can disturb a magnetic field, causing a lack of uniformity in the field and a corresponding lack of consistency in measurements.
Traditional methods of magnetometer testing introduce additional drawbacks. Typically, magnetometer testing is performed by positioning the magnetometer within a set of coils that form the magnetic field. The coils are typically started and stopped repeatedly as sensor devices are placed within and removed from the magnetic field. The coils are inductors, and therefore introduce problems related to overshooting the desired magnetic field strength and then have a dampened oscillation as the magnetic field comes to a steady-state. Magnetic field overshoots can, in some cases, expose the magnetometer to magnetic field strength greater than that for which the magnetometer is designed. Further, the time taken for the magnetic field to come to a steady-state can slow the testing and trimming process for the magnetometers.
It is therefore desirable to have a sensor testing methodology that simplifies the mechanisms required to test each of the types of sensors within a package, improves the testing and trimming cycle time for each sensor package, and enhances the accuracy of testing and trimming for finished, singulated products.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.